1. Field of the Invention
This invention relates in general to pumps and more particularly to an improved liquid elevating mechanism for use with pressure wave operated pumps.
2. Description of the Prior Art
Pressure wave operated pumps of the type commonly used, for example, in pumping liquid, such as water and oil, to the ground surface from subterranean sources of the liquid are of two basic classes, namely those which operate on hydraulic pressure waves and those which operate on what is referred to as sonic pressure waves.
In the case of hydraulic pressure wave operated pumps, an above ground power input mechanism is operated to cyclically impact a column of liquid which extends downwardly through a first pipe to a subterranean liquid elevating mechanism. By impacting the column of liquid, hydraulic pressure wave pulses are generated and transmitted by the liquid column to reciprocally operate the below ground liquid elevating mechanism. The liquid elevating mechanism includes a plunger, or similar mechanism, having a central passage with a check valve in the lowermost end. When the hydraulic pressure waves impact on the plunger causing it to move downwardly, the check valve will be opened to admit the liquid to be pumped into the central passage of the plunger, and the subsequent upstroke of the plunger, i.e., between each hydraulic pressure wave, causes a general upward movement of the liquid in the central passage of the plunger, and this liquid moves to the ground level through a second pipe. Examples of specific pumps which operate on this general principle are disclosed, for example in U.S. Pat. Nos.: 2,379,539, 2,572,977, 2,751,848 and 3,277,831.
Pumps which operate on which is commonly referred to as sonic pressure waves have a single tube, referred to as a production tube, extending between the above ground power input mechanism and the below ground liquid elevating mechanism. The power input mechanism is of special configuration to cyclically impact the column of liquid in the production tube and produce pressure wave pulses which are believed to be sonic in nature. Those sonic pressure waves move downwardly about the periphery of the liquid column to reciprocally operate the plunger in the liquid elevating mechanism in the same manner as described above, and the sonic pressure waves are reflected upwardly and centrally through the production tube to carry the liquid being pumped to the ground surface. Examples of pumps which operate on this basic principle are disclosed in U.S. Pat. Nos.: 4,295,799 and 4,341,505.
In both of the above described types of pumps, the plungers of the underground liquid elevating mechanisms must be biased upwardly an amount which corresponds approximately to the downwardly exerted forces bearing thereon as a result of the head pressure of the column of liquid. The upward biasing force applied to the plunger must be slightly greater than the head pressure so that the plunger will move upwardly to the limit of its travel between each pressure wave, and this bias must be just slightly greater than the head pressure so that the pressure waves will reciprocally drive the plunger to the downward limit of its travel.
The head pressure exerted on the plungers of the liquid elevating mechanism is, of course, a function of the depth of the well and the counterbalancing biasing force applied to the plunger must be reduced or increased in accordance with the depth of the well. Heretofore the counterbalancing biasing force was accomplished by compression spring assemblies which were added to or removed from the liquid elevating mechanism as needed. There are several problems associated with the compression spring assemblies. The first problem is obtaining springs of relatively consistent force exerting value so that an accurate and known consistent amount of biasing force can be added to or removed from the liquid elevating mechanism. The second problem concerns the spring mounting apparatus per se, which must be configured to position the springs so that they cumulatively bear against the plunger and yet the apparatus must be relatively small in diameter so as not to cause problems with regard to the passage of the liquid elevating mechanism through the well casing during installation and removal from a well. Further, the spring assemblies should be as light in weight as possible, so as not to cause problems with regard to the suspended supporting of the liquid elevating mechanism within the well. Also, the springs must be capable of withstanding the deteriorating effects of the liquids being pumped, such as sour crude oil, must resist embrittlement, and the like. And of course, springs meeting such requirements are expensive.
Therefore, a need exists for a new and useful liquid elevating mechanism which overcomes some of the problems and shortcomings of the prior art.